In present use, a flash memory can be used as a data storage. Traditionally, the flash memory is usually a two-dimensional array structure. In recent years, there have been many three-dimensional memory devices, which have increased the amount of data stored per unit area. The key principle of flash memory lies in that, via high voltage writing, a flash memory can store data in the critical voltage mode of the transistor. Furthermore, a flash memory can also be used as a computing unit in a neural network circuit.
However, the disadvantage with the use of traditional planar flash memory is that its transistor can only store one analog datum through the threshold voltage. And the traditional FinFET structure has the same gate voltage on both sides, and both ends must be read/write at the same time. Furthermore, although the 3D memory arrays today may increase the storage density per unit area, they are extremely costly to develop and are not suitable for NOR connections (source grounding) of neural networks.